From 8f1a91aeff400d572857895b7f5e863ec5a4d93e Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Mon, 26 Sep 2022 15:03:53 -0400 Subject: [PATCH] runtime: portable access to sigev_notify_thread_id MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously, libgo relied on the _sigev_un implementation-specific field in struct sigevent, which is only available on glibc. This patch uses the sigev_notify_thread_id macro instead which is mandated by timer_create(2). In theory, this should work with any libc implementation for Linux. Unfortunately, there is an open glibc bug as glibc does not define this macro. For this reason, a glibc-specific workaround is required. Other libcs (such as musl) define the macro and don't require the workaround. See https://sourceware.org/bugzilla/show_bug.cgi?id=27417 This makes libgo compatible with musl libc. Based on patch by Sören Tempel. Change-Id: I0924a53d5212730ebc395ecf9199f85967be8cc6 Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/434755 Reviewed-by: Cherry Mui Reviewed-by: Than McIntosh --- libgo/go/runtime/os_linux.go | 12 +++++++++++- libgo/runtime/go-signal.c | 18 ++++++++++++++++++ 2 files changed, 29 insertions(+), 1 deletion(-) diff --git a/libgo/go/runtime/os_linux.go b/libgo/go/runtime/os_linux.go index 96fb1788..2b2d827c 100644 --- a/libgo/go/runtime/os_linux.go +++ b/libgo/go/runtime/os_linux.go @@ -22,6 +22,12 @@ type mOS struct { profileTimerValid uint32 } +// setSigeventTID is written in C to set the sigev_notify_thread_id +// field of a sigevent struct. +// +//go:noescape +func setSigeventTID(*_sigevent, int32) + func getProcID() uint64 { return uint64(gettid()) } @@ -52,9 +58,12 @@ const ( ) // Atomically, +// // if(*addr == val) sleep +// // Might be woken up spuriously; that's allowed. // Don't sleep longer than ns; ns < 0 means forever. +// //go:nosplit func futexsleep(addr *uint32, val uint32, ns int64) { // Some Linux kernels have a bug where futex of @@ -73,6 +82,7 @@ func futexsleep(addr *uint32, val uint32, ns int64) { } // If any procs are sleeping on addr, wake up at most cnt. +// //go:nosplit func futexwakeup(addr *uint32, cnt uint32) { ret := futex(unsafe.Pointer(addr), _FUTEX_WAKE_PRIVATE, cnt, nil, nil, 0) @@ -365,7 +375,7 @@ func setThreadCPUProfiler(hz int32) { var sevp _sigevent sevp.sigev_notify = _SIGEV_THREAD_ID sevp.sigev_signo = _SIGPROF - *((*int32)(unsafe.Pointer(&sevp._sigev_un))) = int32(mp.procid) + setSigeventTID(&sevp, int32(mp.procid)) ret := timer_create(_CLOCK_THREAD_CPUTIME_ID, &sevp, &timerid) if ret != 0 { // If we cannot create a timer for this M, leave profileTimerValid false diff --git a/libgo/runtime/go-signal.c b/libgo/runtime/go-signal.c index 528d9b6d..aa1b6305 100644 --- a/libgo/runtime/go-signal.c +++ b/libgo/runtime/go-signal.c @@ -183,6 +183,24 @@ setSigactionHandler(struct sigaction* sa, uintptr handler) sa->sa_sigaction = (void*)(handler); } +#ifdef __linux__ + +// Workaround for https://sourceware.org/bugzilla/show_bug.cgi?id=27417 +#ifndef sigev_notify_thread_id + #define sigev_notify_thread_id _sigev_un._tid +#endif + +void setSigeventTID(struct sigevent*, int32_t) + __asm__ (GOSYM_PREFIX "runtime.setSigeventTID"); + +void +setSigeventTID(struct sigevent *sev, int32_t v) +{ + sev->sigev_notify_thread_id = v; +} + +#endif // defined(__linux__) + // C code to fetch values from the siginfo_t and ucontext_t pointers // passed to a signal handler.